The invention resides in a connection box for an internal combustion engine with a charge air cooling arrangement and with a two-stage combustion air charging system and also to an internal combustion engine including such a connection box and charge air treatment.
In particular in connection with Diesel internal combustion engines combustion air charging is well established for increasing engine power output, efficiency and also for reduced exhaust gas emissions as a result of improved combustion of the Diesel fuel. This is actually necessary for complying with official exhaust gas emission limits. Depending on requirements in particular in connection with large Diesel engines, a two-stage charging system, that is a low-pressure stage and a high pressure stage charging system preferably but not necessarily in combination with exhaust gas recirculation has been found effective to consider the above aspects with a view to further improvements. However, because of the high pressure charge air, low pressure charge air and, if applicable, exhaust gas recirculation arrangements including the necessary charging fluid flow passages the design of a two-stage charging arrangement, in particular with exhaust gas recirculation, generally requires a relatively large installation space. For each charging stage, in addition to a turbocharger which includes an exhaust gas driven turbine and a charge air compressor, also a suitable cooling arrangement is needed for cooling the compressed charge air flows and/or exhaust gas recirculation flows before their admission to a combustion chamber of the internal combustion engine.
With a two-stage charging arrangement, at least a first and a second charge air cooler need to be included in a cooling arrangement. It may also be expedient to provide at least one exhaust gas recirculation cooler. In the various coolers pressure losses of the charging fluids should be kept as small as possible. This applies also to the exhaust gas conducted through an exhaust gas recirculation cooler. In the present case, in particular flow losses of a charge air flow to and from a charge air cooler should be kept low and, additionally, a heat exchange in a charge air cooler should be improved. To this end, a charge air cooler of a cooling arrangement of the type described above is connected to a charge air ducting structure via an air connection box. In this way a flow cross-section of the charge air guide structure can be adapted to a flow cross-section of the charge air cooler. A connection box may also provide a diffuser effect which serves to reduce substantially the flow speed and pressure losses by widening the flow cross-section.
The installation of the above components on an internal combustion engine does not only need to comply with requirements in respect to the available installation space but, in addition, flow-based requirements must be satisfied for optimizing engine power and exhaust gas discharge of an internal combustion engine. Such requirements are increasingly important in connection with smaller sizes of large Diesel engines. This concerns in particular the arrangement of a first and a second charge air cooler together with the usually space consuming connection boxes of a cooling arrangement in charge air guide structure. The provision of an intake-side and an exhaust-side air connection box at a first and a second charge air cooler has been found to be problematic in connection with two-stage charging of an internal combustion engine if in addition to flow guide requirements also the installation space for the cooling arrangement is tight.
A comparably compact flow guide structure for the cooling arrangement would therefore be desirable. The charge air guide structure with connection box, cooler arrangement for the charge air of a two-stage charging system and its installation on an engine should therefore require as little installation space as possible but still provide for advantageous flow conditions for the charge air supply of an associated internal combustion engine.